The methods and devices for determining quantity and size of the particles and small bodies are now well known, and it is also well known that powerful light or laser and optical system or mirror can be, and have been, heretofore used to achieve particle size and particle quantity measurements. Such devices using light scattering are well known and described in the articles: R. G. Knollenberg, B. Schuster--"Detection and Sizing of Small Particles in Open Cavity Gas Laser," Applied Optics, Vo.11, No.7, November 1972, pp.1515-1520; R. G. Knollenberg--"An Active Scattering Aerosol Spectrometer," Atmospheric Technology, No.2, June 1973, pp.80-81; R. G. Knollenberg--"Active Scattering Aerosol Spectrometry," National Bureau of Standards Special Publication, No.412, October 1974, pp.57-64; R. G. Knollenberg, R. E. Luehr--"Open Cavity Laser Active Scattering Particle Spectrometry from 0.05 to 5.0 Microns," Fine Particles, Aerosol Generation Measurement, Sampling and Analysis, Academic Press, May 1975, pp.669-696; R. G. Knollenberg--"Three New Instruments for Cloud Physics Measurements: The 2-D Spectrometer, the Forward Scattering Spectrometer Probe, and the Active Scattering Aerosol Spectrometer", American Meteorological Society, International Conference on Cloud Physics, July 1976, pp. 554-561; R. G. Knollenberg--"The Use of Low Power Laser in Particle Size Spectrometry", Proceeding of the Society of Photo-Optical Instrumentation Engineers, Practical Applications of Low Power Lasers, Vo.92, August 1976, pp.137-152; R. G. Knollenberg--"The Measurement of Particle Sizes Below 0.1 Micrometers", Journal of Environment Science, January-February, 1985, pp. 64-67.
The reference in these articles is made to the devices and methods of particulate measurement utilizing an open cavity laser. These methods and devices use the imaging systems which are based on lens use, the same as it mentioned, for example, in the U.S. Pat. No. 4,798,465 and in the U.S. Pat. No. 4,140,395 of the prior art.
The other devices mentioned in prior art (for example, U.S. Pat. No. 4,606,636) use a non-divergent quadric reflector. These devices use a paraboloidal sphere as mirror.
Yet in other prior art (for example, such as U.S. Pat. No. 4,523,841 and U.S. Pat. No. 5,467,189) we can find the devices (the sensors) with the elliptical mirrors instead the lens systems or the non-divergent mirrors.
All these devices, mentioned in the prior art above, use very narrow light (laser) beam, but not consider the width of the particles flow. It means that just particles which intersect the narrow light beam at the focal point (focus) are considered for counting and measuring processes. As shown on FIG. 1, the scattered light related to non-focused particles, mentioned of the above, will be stochastically reflected (the scattered light will be not directed to the second focal point 9 of the mirror system 4, where is located a light detection means 5). It is understood that the scattered light related with the particles, which will not pass through the focus 8, create the non-focused scattered light 7, which will not be detected by light detection means 5.
The counting and measuring device (sensor) by U.S. Pat. No. 5,515,164 uses increased cross-sectional size of the particle flow. On FIG. 2 is shown the part of the sensor which has specially increased cross-sectional area of the particle flow exit mouth 72, extended along the light beam axis 2. FIG. 2 also presents some configurations (forms) of the particle flow exit mouth 72, according to mentioned U.S. Pat. No. 5,515,164. Such devices provide counting and measuring only minimal portion of assaying air, because only particles of the particle flow, which pass through the point of the intersection with very narrow light beam and exactly at the focal point 8 (first focus) will creat a focused scattered light 6 and will be detected by light detection means 5. All other particles of the particle flow can not be counted, measured and relative non-focused scattered light 7 will create highest background (light noises).
Also the turbulence, used in mentioned above device creates the air-eddying movements, which can lift already counted and measured particles for frequentative counting and measuring, thereby creating incorrectness of the resulting information.
The same regards to the devices, referring to mentioned above U.S. Pat. No. 4,798,465 and No. 4,140,395, which use the optical systems 11 (for example, lenses). As we can see from FIG. 3, the non-focused scattered light 7 will be undetected and thereby will also create the light noises, as was mentioned for the device, using mirrors.
On FIG. 4 is presented the device, using non-divergent quadric mirror, regarding U.S. Pat. No. 4,606,636. From FIG. 4 we see that the non-focused scattered light 7 creates the light noises too.
Everything described of the above can be applied to the liquid particle (contaminations) counters, using uninterrupted (undivided) liquid flow trace instead divided particle flow trace, as it was mentioned for airborne particle counting and measuring devises.
Some information about a prior art method and devices can be also obtained from: Peters--"20 Good Reasons to Use In Situ Particle Monitors", Semiconductor International, November 1992, pp.52-57; Busselman et al.--"In Situ Particle Monitoring in a Single Wafer Poly Silicon and Silicon Nitride Etch System", IEEE/SEMI Int'l Semiconductor Manufacturing Science Symposium, 1993, pp.20-26 and U.S. Pat. No. 5,083,865 (Feb. 28, 1992).
It is known, that integrated circuits (chips) and semiconductors have been produced in "clean rooms". The air in such "clean rooms" should be very well cleaned. The continuing tendencies of the improvement of circuit integration and degree of microminiaturization require corresponding improvements of the environment in "clean rooms" and efficiency of the measuring devices. And now, as known from prior art, the sensitivity of the counting and measuring devices should be at least as small as 0.1 Micron.
Thus, the non-focused scattered light in the mentioned above devices of a prior art creates the light background (light noises) inside the sensor, creating incorrectness of resulting information about outside environment and additionally light noise limits the sensitivity of such devices.